coolant in crankcase

[klrh2o]

Hi my name is Steve, I need advice for my wife's klr250. I rebuilt the top end. It runs fine, except that coolant/water is leaking into the crank case. It doesn't smoke, sounds good and idles fine. When we acquired the bike, it had been sitting dis-assembled for a year. The previous owner ran it hot. I replaced the mechanical seal on water pump. I'm wondering if anyone can tell me how to determine if the head gasket is leaking without tearing it back down. Or if there is some other way water can be getting into crank- case. Any help is appreciated.